Our company is recently being told by some of our clients that they are not receiving our emails - this is new.  We have IMAP setup and are bcc-ing other cloud-based applications (like gmail) that ARE receiving our emails but the end clients don't seem to be.  Is there any setting that anyone has used that could help with this?  I've been reading about SPF but not sure I should do that or not at our root domain.

Thanks in advance!